In recent years, a system has been proposed wherein a portable terminal accesses a contents server present on a network (particularly the Internet) to fetch information from the network.
FIG. 27 shows the construction of a system wherein a portable terminal M accesses a contents server S present on a network.
As shown in FIG. 27, in order to achieve the access from the portable terminal M to the contents server S present on the network, a specialty server called a gateway server G is disposed at a point of access to the network.
The gateway server G is connected to the portable terminal M through a radio communication channel. The communication through the radio communication channel is performed, for example, using a communication protocol called WAP (wireless application protocol) optimized for the characteristics of wireless and portable terminals. On the other hand, communication between the contents servers S present on the network and the gateway server G is performed based on a standard protocol of this network [for example, in the case of the Internet, standard protocols for the Internet, such as HTTP (hyper-text transfer protocol) or TCP (transmission control protocol)].
The gateway server G has the function of performing protocol conversion between the communication protocol in the radio communication channel and the standard protocol in the network on which the contents server S is present, the function of converting data, for example, the function of, when information held in the contents server on the network is a document written in the form of HTML (hypertext markup language), converting the document in the HTML form to a document in a WML (wireless application language) form used in WAP, and the function of, for example, when the document held in the contents server S on the network is a WML document in a text form, converting WML document to a binary form to compress the data.
Next, a method for access from a portable terminal M to a contents server S on a network in a mobile communication system having the above construction will be explained in conjunction with FIG. 28.
At the outset, when the power of the portable terminal M is turned on, the positional information of the portable terminal M is cataloged in a positional information database P through the nearest base station. Next, when a call is made from the portable terminal M to the phone number of a previously cataloged access point, connection between the portable terminal M and a gateway server G carrying this access point is established.
In the request for access to a contents server S, a method may be used wherein the request for access is notified in a suitable radio communication protocol, for example, HTTP or WAP, to the gateway server G, and a contents server S can be selected and designated, for example, by URL (uniform resource locator).
In a mobile communication system having the above construction, however, even when the contents server S has suffered from fault such as down and thus cannot provide a service to the user of the portable terminal M, the user cannot previously learn the fault before an attempt to access the contents server S from the portable terminal M.
For this reason, when the user of the portable terminal M has made a request for access to the contents server S suffering from fault, the user can learn the inactive state of the service provided by the contents server S only through a phenomenon of access time-out in the portable terminal M caused by a failure of response from the contents server S. The access time-out takes place in two cases, that is, the case where the number of requests for access to the contents server is too large to access the contents server, and the case where the contents server suffers from fault. The user cannot judge whether the access time-out is attributable to the excessively large requests for access to the contents server or to the down of the contents server. Therefore, the user can learn the down of the contents server only after a large number of attempts to access the contents server. This leads to loss of a lot of time.
In order to solve this problem, Japanese Patent Laid-Open No. 249249/1996 (prior art 1) proposes a message repeater and a message repeating method.
Specifically, the prior art 1 proposes a message repeater for a relay of a message between at least one client for sending a request message and at least one server for receiving the contents of the request message and sending a message respondent to the request message, said message repeater comprising: management means for managing the state of the server; and control means for controlling the relay of the message based on the contents of the management means.
The management means comprises: a dialog identifying information storage means which uniquely identifies a message respondent to a request message and, in addition, stores dialog identification information for distinguishing the client as the requester from the send destination server and, when a request for cataloging or deletion of the dialog identification information has been issued, catalogs or deletes the dialog identification information; and a server state monitor means which monitors the state of each server and, when fault of a server has been detected, sets the state of the server, which is managed within this means, as fault and makes an instruction for the response of a message of fault to the request message regarding the dialog identification information for the fault server.
Further, Japanese Patent Laid-Open No. 214545/1997 (prior art 2), which is relevant to the invention in the technical field, proposes a network communication control system.
Specifically, the prior art 2 discloses a composite network system wherein a plurality of networks connecting a plurality of stations to each other are connected to each other through a connecting device, said connecting device comprising: connection control means for controlling send/receive of data between the plurality of connected networks; network monitor means which monitors the state of the stations connected to the plurality of networks to collect the information of the status of the stations; state information storage means for holding the state information collected by the network monitor means; judgment means which reads the state information stored in the state information storage means to judge whether or not the send destination of data sent from each station is normal; fault notification means which, when the data send destination station has been judged by the send judgment means to be abnormal, sends a fault response to the data sender station; send failure station address storage means which, when the data send destination station has been judged by the send judgment means to be abnormal, stores the address of data send destination station and the address of the sender station; undelete judgment means which, based on an instruction from the network monitor means, judges, from information stored in the state information storage means and the send failure station address storage means, whether or not the data send destination station has been undeleted; and undelete notification means which, when the data send destination station has been judged by the undelete judgment means to be in an undelete state, sends an undelete response to the data sender station.
In both the above prior art techniques, however, the terminal side can recognize only the state of the server, to which the access has been requested by the terminal, and cannot recognize the state of other servers on the network.
Further, in both the above prior art techniques, until the terminal makes a request for access to a predetermined contents server, the gateway server does not send, to the terminal, information about whether or not the designated contents server is down.
Therefore, before the send of a request for access, the terminal side cannot previously recognize the state of contents servers present on the network. Thus, for the user of the portable terminal, wasteful communication takes place, and, hence, the user should pay wasteful communication charge. On the other hand, for the system side, wasteful line connection disadvantageously lowers line utilization.